In general, the construction of sanitary absorbent articles, such as panty liners, diapers, incontinence articles and sanitary napkins, includes a body-facing layer, a garment-facing layer and an absorbent core positioned between the two. These different layers are kept together in a variety of different manners such as via crimping, thermal bonding and/or adhesive positioned between the layers. In the case of panty liners, incontinence articles and sanitary napkins, the garment-facing surface of these articles also includes a positioning adhesive thereon for securing the sanitary absorbent article to a wearer's undergarment.
Traditional manners of applying bonding adhesive between the different layers of material, or applying positioning adhesive to the garment facing surface of the napkin, involve either applying the adhesive via a printing operation (i.e. via contact deposition) or via a spraying operation. In the case of positioning adhesive, the adhesive can be applied either to the material of the garment facing surface directly, or to a release paper that transfers the positioning adhesive to the garment facing surface when the two are put into communication with each other. Each of these traditional methods of applying adhesive have numerous deficiencies, some of which will be described below.
For example, devices that print adhesive onto a substrate via contact deposition generally include a printing roll that includes indentations thereon for receiving adhesive to be printed onto the substrate. As the substrate moves past the printing roll, the adhesive contained within the indentations of the printing roll is printed onto the substrate via contact deposition. Unfortunately, a common deficiency with such printing devices is that in order to maintain the adhesive in a state wherein it can easily be printed onto a substrate, the printing roll is kept at a relatively high temperature. Often, the substrates of material that are to be incorporated into a sanitary absorbent article are quite fragile and delicate and are thus often damaged (i.e. melted) when the substrate moves past the heated printing roll. This results in damaged materials, and the need to shut down the printing device until a new substrate can be passed through the printing machine.
In order to avoid the deficiencies with such printing devices, another method of applying adhesive to a substrate is to use a spraying device, that sprays adhesive onto a substrate. However, a deficiency with devices used to spray adhesives onto substrates for sanitary absorbent articles, is that the adhesive cannot be continuously applied in accordance with complex shapes and patterns. Instead, the devices that spray adhesive onto a substrate simply apply the adhesive in accordance with a matrix of dots and/or lines. Given the asymmetric, often curved shape of many sanitary absorbent articles currently being manufactured today, this manner of applying adhesive is not able to apply sophisticated non-uniform, and often non-linear patterns of adhesive onto many sanitary absorbent articles.
Traditionally, sanitary absorbent articles (excluding diapers) have been secured to a wearer's undergarment. In many cases, however, it is desirable to adhere the absorbent article directly to a wearer's skin instead of to the wearer's undergarment. In order to adhere the absorbent article directly to a wearer's skin, a complex, non-linear pattern of adhesive is required on the body-facing layer of the material. Unfortunately, traditional methods and apparatuses for applying adhesive have not been able to achieve the shapes and or patterns of adhesive that would be required in order to adhere a sanitary absorbent article directly to a wearer's skin.
In the context of the above, it can be appreciated that there is a need in the industry for a method and apparatus for applying bonding and/or positioning adhesive to a substrate that allows complex shapes and or patterns of adhesive to be applied to the substrate while alleviating, at least in part, the deficiencies associated with the existing methods and devices.